Apparatus and method for asymmetrical coast control of an endodontic motor

ABSTRACT

An apparatus for controlling asymmetrical coasting of an endodontic reciprocating motor includes a controller operatively connected to the endodontic motor. The controller may include a processing unit that is configured to direct the rotation of the endodontic motor in the forward direction for a coast time and configured to direct the rotation of the endodontic motor in the reverse direction for a coast time. The forward coast time is separately calculated from the reverse coast time. A method for asymmetrically coasting a reciprocating endodontic motor includes rotating an endodontic motor in a forward direction and calculating a forward coast time for the forward direction and coasting the endodontic motor in the forward direction for the calculated forward coast time. After coasting the endodontic motor in the forward direction, the endodontic motor is rotated in a reverse direction. The reverse coast time is different than the forward coast time.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/786,565 filed Mar. 6, 2013, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/608,946, filed on Mar. 9,2012, the disclosures of which are expressly incorporated by referenceherein in their entirety.

TECHNICAL FIELD

The present invention relates generally to an apparatus and a method forenhancing the performance of an endodontic motor for use duringendodontic treatment.

BACKGROUND

Root canal therapy may include clinical instrumentation that is drivenby an endodontic motor. Endodontic motors have traditionally beendesigned to maintain constant rotation of between 300 RPM and 1000 RPM.Typically, a clinician sets the rotation speed. Despite the applicationof variable torque and friction to the motor during use, constant motorrotation is often maintained by a feedback control loop that dynamicallymonitors and then acts to maintain the speed of the motor. In thismanner, the power output to the endodontic motor varies in accordancewith the variable torque and friction observed by the motor to maintainthe preset motor speed.

More recently, developments within the endodontic field suggest aperformance benefit from a reciprocating endodontic motor. Reciprocatingendodontic motors drive the rotor and attached endodontic drill or filethrough a clockwise rotation and then a counterclockwise rotation. Thisclockwise-counterclockwise rotation cycle may be repeated very rapidlyduring treatment. By way of example, the reciprocating endodontic motormay rotate a file clockwise 160 degrees followed by a counterclockwiserotation of 40 degrees. This reciprocating motion may be repeated withany combination of clockwise and counterclockwise rotations of differingdegrees to create novel and complex filing cycles. Moreover, byintroducing two directions of movement, the attached drill or file hastwo potentially useful directions, each rotation direction of which iscapable of specialization. For instance, a file may be designed for dualuse such that it may cut while rotating clockwise, but grind or buffwhile rotating counterclockwise.

A further modification to the reciprocating endodontic motor is a coastfeature. In this regard, at the end of a clockwise or counterclockwiserotation, the motor and attached file will coast under only theinfluence of its own momentum. For example, an endodontic motorprogrammed with the coast feature may be programmed to drive a filethrough a 120 degree clockwise rotation followed by an 80 degreecounterclockwise rotation. Following the 120 degree clockwise rotation,the endodontic motor and attached file will continue to rotate, but suchrotation will be the result of coasting beyond the specified clockwiserotation. Thus, coasting occurs prior to beginning a counterclockwiserotation of 80 degrees. Regardless of the prescribed angular values, thecoast feature permits additional, though unpowered, rotation of theendodontic motor. The amount of such additional rotational coast isdynamically determined and may depend on the time permitted to coast,the angular momentum of the system, and/or the amount of frictionencountered by the system. It will be appreciated that generally angularmomentum of the motor increases coast time while increased frictionreduces coast time.

As applied to reciprocating endodontic motors, the coast feature is adesirable feature because it allows the motor and file to dynamicallyand automatically respond to various and complex environmental factors,including the specific anatomy encountered during root canal therapy.Rather than the traditional preset and forced control drive which forcesa highly prescribed motion, the coast feature allows for greaterflexibility of rotational movement. For instance, where the file isspinning freely within the root canal, coast will allow the file tocontinue spinning while also cutting efficiently to reduce the time tocomplete the procedure. On the other hand, where the file encountersincreased friction due to resistance, coast will decrease the rotationof the endodontic motor to reduce torsional and bending loads applied tothe file. In either case, the coast feature provides significantprocedural benefits.

Presently, a clinician must choose an amount of coast that issymmetrically applied to the tool. That is, coasting following aclockwise rotation is the same as the coasting following acounterclockwise rotation. Unfortunately, different tools createdifferent frictional forces, which, in turn, affect the amount ofoptimal coast for a counterclockwise rotation and a clockwise rotation.For instance, a file cutting in the clockwise direction will encountergreater friction and resistance than the same file which produces abuffing action in the counterclockwise direction. Such divergent usesmay force a clinician to choose a coast for either cutting or buffing,but not both simultaneously. Thus, a clinician desiring a particularcoast in the clockwise direction must also accept this coast in thecounterclockwise direction due to the nature of such symmetrical coastcontrol. Identical coast settings are not necessarily advantageous,because significant rotation in the counterclockwise direction may leadto undesirable procedural phenomena such as extrusion of canal debrisout of the canal apex, creating post operative pain for the patient.

There is a need for an apparatus and method for use in endodonticprocedures, such as root canal therapy, that addresses presentchallenges and characteristics such as those discussed above.

SUMMARY

The present invention overcomes the foregoing and other shortcomings anddrawbacks of endodontic motor control systems heretofore known. Whilethe invention will be described in connection with certain embodiments,it will be understood that the invention is not limited to theseembodiments. On the contrary, the invention includes all alternatives,modifications and equivalents as may be included within the spirit andscope of the present invention.

In accordance with the principles of the present invention, an apparatusfor controlling asymmetrical coasting of an endodontic reciprocatingmotor comprises an endodontic motor capable of rotating a tool in aclockwise direction and in a counterclockwise direction. The apparatusfurther comprises a controller operatively coupled to the endodonticmotor. The controller is capable of transmitting electronic signals tothe endodontic motor to change the direction of rotation of the toolfrom the clockwise direction to the counterclockwise direction. Thecontroller is capable of controlling a forward coast time during whichthe endodontic motor coasts in the clockwise direction and controlling areverse coast time during which the endodontic motor coasts in thereverse direction. The forward coast time is different from the reversecoast time.

In one embodiment, the controller includes a processing unit operativelyconnected to the endodontic motor. The processing unit is configured todirect the rotation of the endodontic motor in the forward direction fora forward coast time and configured to direct the rotation of theendodontic motor in the reverse direction for a reverse coast time. Theprocessing unit is configured to calculate the forward coast timeseparately from the reverse coast time.

In accordance with the principles of the present invention, a method forasymmetrically coasting a reciprocating endodontic motor, comprisesrotating an endodontic motor in a forward direction and determining aforward coast time for the forward direction. The method furtherincludes coasting the endodontic motor in the forward direction for thedetermined forward coast time, and, after coasting the endodontic motorin the forward direction, rotating the endodontic motor in a reversedirection. The method further includes determining a reverse coast timefor the reverse direction separately from the determined forward coasttime. The reverse coast time is different than the forward coast time.The method further includes coasting the endodontic motor in the reversedirection for the determined reverse coast time.

In one embodiment, determining the forward coast time includescalculating the forward coast time based on a forward coast setting.

In one embodiment, determining the reverse coast time includescalculating the reverse coast time based on a reverse coast setting.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the invention.

FIG. 1 is a perspective view of one embodiment of an apparatus forcontrolling asymmetric coasting of an endodontic motor;

FIG. 1A is a block diagram of the apparatus of FIG. 1; and

FIG. 2 is a flow chart of one embodiment of a method for asymmetricallycoasting a reciprocating endodontic motor according to another aspect ofthe present invention.

DETAILED DESCRIPTION

With reference to FIG. 1, in one embodiment of the present invention, anapparatus for controlling asymmetric coasting of an endodonticreciprocating motor 10 includes a console 14 and an on/off controlswitch 16. The console 14 may be operatively coupled to a motorhandpiece 12 that is configured to couple to and rotate a tool for usein endodontic treatment. In particular, as is described below, theapparatus 10 is configured to rotate the tool in both the clockwise andcounterclockwise directions during a single endodontic operation. Theclockwise and counterclockwise rotations may be iteratively repeatedover very short periods of time, for example, on the order of seconds orless. The apparatus 10 is also configured to allow the tool to coast ineach of the clockwise and counterclockwise directions for apredetermined period of time. This may be referred to as the “coasttime” herein. Further, as used herein, the term “coast” means that therotation of the tool is unpowered. In other words, rotation of the toolis not being forced or acted upon by the apparatus 10. Allowing the toolto coast for a long period of time may result in the tool coming to restor a complete stop without internal braking of the rotation thereof. Bycontrast, coasting does not include intentionally reducing the rotationrate of the tool by braking the motor or by other means internal to theapparatus. However, friction inherent in the construction of thehandpiece 12 and between the tool and its environment, such as a toothsurface, is contemplated.

In the representative embodiment shown, the motor handpiece 12 isoperatively coupled to the console 14 via a cable 18. As is known, thecable 18 may transmit electrical or mechanical power and provide apathway for electrical feedback from the motor handpiece 12 to theelectronics (not shown) housed within the console 14. It will beappreciated that the motor handpiece 12 may not require a cableconnection to the console 14, as cordless-type motor handpieces areknown in the art. Similarly, the on/off control switch 16, asrepresented by the foot pedal shown, may be operatively coupled to theconsole 14 and associated electronics via a power cable 20. A clinicianmay utilize the control switch 16 to turn the electrical power to themotor handpiece 12 on and off during endodontic treatment.

With continued reference to FIG. 1, in one embodiment, the motorhandpiece 12 includes a motor 22 and a gearbox 24 operatively coupled tothe motor 22. Motor handpieces that may be coupled to the apparatus 10are known in the art and include brushless DC motors. As is known, thesemotors may contain sensors by which the rotor rotation is monitored, forexample. The gearbox 24, which may be referred to as a contra angle, mayfurther include a head 26 that is configured to hold an endodontic tool28, such as, an endodontic file. Energizing the motor 22 causes rotationof a rotor which, in turn, rotates the linkage in the gearbox 22 andultimately rotates the tool 28 for use in treatment. By way of example,the gearbox 24 may have a gear ratio of 4:1, 8:1, 18:1, or 20:1.Alternatively, the gearbox 24 may have a ratio of 1:10. It will beappreciated that other endodontic tools may be utilized with theapparatus for controlling asymmetrical coasting of an endodonticreciprocating motor 10. Thus, in one embodiment of the invention, thetool 28 is rotated in one direction for a predetermined number ofrotations or time, electric power to the motor 22 is shut off orremoved, which allows the tool 38 to coast for a predetermined coasttime, and, once the predetermined coast time is reached, the tool 28 maybe forcibly brought to a stop by braking. Once the brakes are applied,the coast ends. The direction of the tool 28 is then reversed though,according to embodiments of the present invention, the predeterminedcoast time for the reverse direction is different. According toembodiments of the present invention, the coast time following aclockwise rotation of the tool 28 is separately controlled from thecoast time for a counterclockwise rotation of the tool 28.

As introduced above, in one embodiment, the apparatus 10 is configuredto rotate the tool 28 in a clockwise direction and is also configured torotate the tool 28 in a counterclockwise direction. While the clockwisedirection may be referred to herein as the forward direction and thecounterclockwise direction may be referred to as the reverse direction,such reference is merely for the convenience of description andembodiments of the present invention are not limited to any specificassociation between forward or reverse and clockwise orcounterclockwise.

In the representative embodiment shown, the apparatus 10 includes acontrol panel 30 by which a clinician may select an operating mode ofthe apparatus 10. In this regard, the control panel 30 may includenumerous pushbuttons 32 by which the clinician can set parameters thatultimately control the rotation of the tool 28. Once selected, anindividual parameter may be displayed on screen 34. Of the availableparameters, it will be appreciated that the apparatus 10 may be operatedin a clockwise rotation mode, a counterclockwise rotation mode, or areciprocating mode. In one embodiment, in the reciprocating mode,control of the coast time in the forward direction is separate from thecontrol of the coast time in the reverse direction. Thus, in oneembodiment the forward coast time is different from the reversed coasttime, as is described more fully below.

In particular, and in one embodiment of the present invention, theclinician may select a reciprocating mode for operation of the motor 22during endodontic treatment. The reciprocating mode includes coasting ofthe tool in the forward and reverse directions. The coast time in eachdirection may be asymmetric or different. In this regard, the term“asymmetric” refers to the capability of the apparatus 10 to allow thetool 28 to coast for a preset period of time when rotated in theclockwise direction and/or to allow the tool 28 to coast for a presetperiod of time when rotated in the counterclockwise direction. Theapparatus 10 may thus include independently selectable parameters foreach of the clockwise coast and the counterclockwise coast.

In one embodiment and with reference to FIG. 2, once the reciprocatingmode is selected, the clinician may select, via the pushbuttons 32 (FIG.1), a desired coast setting for coast in the forward direction, i.e.,“Forward Coast,” at 40. The clinician may, in addition or alternatively,select (via pushbuttons 32) a desired coast setting for the coast in thereverse direction, i.e., “Reverse Coast,” at 42. The clinician may alsoindependently select a forward motor speed for the endodontic motor 22and/or a reverse motor speed for the endodontic motor 22 at 44 and 46,respectively.

Once the clinician selects the desired parameters, as described above,the apparatus 10 calculates the forward coast time for the forward coastand/or the reversed coast time for the reverse coast at 60. Theresulting forward coast time and/or reverse coast time as indicated at48 are utilized to control coasting of the tool 28 during endodontictreatment. Other factors that may be used by the apparatus 10 to controlthe coasting of the tool 28 may include the angular momentum of theendodontic motor 22 at 52 and/or torsional and frictional forces appliedto the endodontic motor 22 at 50. As is noted in FIG. 2, in oneembodiment, the apparatus 10 may ultimately calculate the amount ofdynamic angular rotation in one or both of the forward and reversecoasts, as is indicated at 54.

As noted above, the clinician may select a coast setting for each of theforward coast and the reverse coast. In general, the coast setting mayaffect the time that the tool 28 coasts in a given direction. In oneembodiment, the desired coast setting for the forward direction isdirectly related to or is numerically scaled to the amount of coast timeobserved by the tool 28 in the forward direction. In other words, if theclinician desires more coast time in a particular rotation direction,the clinician may simply set a relatively greater coast setting, forexample, by activating a pushbutton 32, for that direction. Similarly,the desired coast setting for the reverse direction may be directlyrelated to or be numerically scaled to the amount of coast time observedby the tool 28 when rotating in the reverse direction. In this sense,the clinician may independently select a coast setting for each of theforward and reverse directions that is optimal for a particular tool. Itwill be appreciated that the selection may be based upon the clinician'sexperience with a particular tool, the treatment desired, the patient'sanatomy, among other factors. Ultimately, the selected parameters affectthe amount of dynamic angular rotation during one or both of the forwardand/or reverse coasts as is indicated at 54.

In one embodiment, the coast setting is numerically scaled to increaseor decrease the amount of time the endodontic motor allows for one orboth of the forward and reverse coasts of the tool 28. Thus, byincreasing the coast setting, the permitted dynamic angular travel isincreased or, by decreasing the coast setting, the permitted dynamicangular travel is decreased. By way of example only and withoutlimitation, the numerical scale may include predetermined from values of−7 to +7. In this case, −7 may provide for the least amount of coasttime, and +7 may provide for the most coast time. By way of furtherexample, a setting of −7 may equate to a coast time range from 0milliseconds to 24 milliseconds and a setting of +7 may equate to acoast time range from 60 milliseconds to 90 milliseconds. Coast settingsof from −7 to +7 may fall approximately between the range of 0milliseconds to 90 milliseconds in accordance with one embodiment of theelectronic control algorithm.

In one embodiment, while the apparatus 10 may provide the controls tovary the coast time for both forward and reverse directions per a coastsetting, as described above, the available parameters are not limited tothe coast setting. Rather, with reference to FIG. 2, the apparatus 10may include additional parameters by which the endodontic motor 22 maybe operatively controlled to account for applied torque and friction at50 and/or angular momentum of the handpiece/tool at 52. Such additionalmetrics may be beneficial to promote greater procedural efficiency aswell as to improve the effective life of the endodontic motor 22 and/orthe tool 28.

In one embodiment, and with reference to FIG. 1A, the apparatus forcontrolling asymmetrical coasting of an endodontic reciprocating motor10 includes a controller, which in the representative embodiment is aCPU or a processing unit 70, a memory 72, a motor interface 74, andinput/output (“I/O”) interface 78. The I/O interface 78 may beconfigured to receive data or signals from the control panel 30, and inparticular the pushbuttons 32, and from the on-off control switch 16that are then communicated to the processing unit 70. The I/O interface78 may be configured to output data from the processing unit 70 to thecontrol panel 30, and in particular, to the display 34. Though notshown, other devices external to the housing may include additional userinput devices such as a keyboard, a keypad, a mouse, a microphone, etc.Embodiments of the present invention are not limited to the externaldevices shown. The memory 72 is configured to store a software module oran application 80, such as, an electronic control algorithm, asdescribed below, and an operating system 82. The application 80 andoperating system 82 each generally comprise one or more instructionsstored as program code that may be read from the memory 72 by theprocessing unit 70. The instructions, when executed by the processingunit 70, may cause the processing unit 70 to perform one or moreoperations or calculations to thereby perform the steps necessary toexecute steps, elements, and/or blocks according to various embodimentsof the invention. The memory 72 may represent random-access memory (RAM)comprising the main storage of a computer, as well as any supplementallevels of memory, e.g., cache memories, non-volatile backup memories(e.g., programmable or flash memories), mass storage memory, read-onlymemories (ROM), etc.

The coast setting is operatively implemented via the processing unit 70of apparatus 10. In this regard, the apparatus 10 may include variouspre-programmed operating modes that include predetermined asymmetriccoast times. The modes may be stored in the memory 72 that is accessibleby the processing unit 70. Advantageously, the pre-programmed operatingmodes may include specific parameters for the coast time and therotation rate for each of the forward and reverse rotation directions.These specific predetermined parameters may be based on prior experiencewith a particular tool, a particular motor, and/or a particulartreatment. In one embodiment, the pre-programmed operating modespreclude any changes to either the forward or reverse coast setting bythe clinician. Thus, at least the forward coast setting and the reversecoast setting for a particular pre-programmed operating mode are factorysettings.

Furthermore, it will be appreciated that while the apparatus 10 includesa process unit 70 and other components for controlling the coast of thetool, one of ordinary skill will observe that the controller, which maynot be the processing unit 70, determines the coast of the toolaccording to embodiments of the present invention. The controller mayinclude fixed hardware and electrical timing circuits capable ofcontrolling the forward coast time and the reverse coast time. In thisembodiment, the forward and the reverse coast time may not be adjustableor selectable. Rather, these times are factory settings, similar to thatset out above. Embodiments of the present invention are therefore notlimited to the use of a processing unit, though use of fixed hardwarewould generally preclude software control and would thus makeadjustments to the coast setting substantially more complex.

In view of the apparatus 10 described above, a clinician, who hasselected a particular tool for a particular endodontic procedure maysimply select, via the pushbuttons 32, the desired operating mode thatincludes all of the optimum parameters for that tool and procedure, forexample. Therefore, once the preprogrammed operating mode is selected,the processing unit 70 automatically loads the pre-determined values forthe coast setting with respect to a desired coast time for one or bothof the forward and reverse directions. The processing unit 70 may thenprovide one or more signals to the motor interface 74 that then controlsthe rotation of the motor 22 by regulating the power to the motor 22according to the one or more signals from the processing unit 70. Theapparatus 10 may further include a feedback loop 76 by which rotation ofthe rotor of the motor 22 may be monitored by the motor controller 74and/or the processing unit 70, according to known methods in the art.Feedback electrical signals from the motor 22 may be processed by theprocessing unit 70 and/or the motor interface 74 according to the loop76 so that the processing unit 70 and/or the motor interface 74 maychange the control signal or power to the motor 22 to make adjustmentsto the rotation of the tool 28.

In one embodiment, the apparatus 10 includes an electronic controlalgorithm 80. In particular, the electronic control algorithm 80 may bestored in the memory 72 and when the clinician desires control of theforward coast time and/or the reverse coast time by the processing unit70, the control algorithm 80 may accessed and utilized by the processingunit 70. In one embodiment, and with reference to FIG. 2, the processingunit 70 calculates the forward coast time and/or the reverse coast timevia the electronic algorithm at 60. As shown, this calculation mayinclude various parameters, including the coast setting at 40 and 42 andthe angular speed for one or both of the forward and reverse directionsat 44 and 46. The output from this calculation is the forward coast timefor the forward coast and the reverse coast time for the reverse coast,as is indicated at 48.

With continued reference to FIG. 2, a representative electronic controlalgorithm for controlling a reciprocating endodontic motor is shown at60. The electronic control algorithm may provide the necessary output tocause the endodontic motor to rotate for a predetermined amount of coasttime in one or both of the forward and reverse directions. As shown, theelectronic control algorithm calculates the forward coast time andreverse coast time via the preset algorithm:Forward Coast Time [sec]=(−0.00005)(Forward AngularSpeed)+(0.08)+(0.0044)(Forward Coast Setting)andReverse Coast Time [sec]=(−0.00005)(Reverse AngularSpeed)+(0.08)+(0.0044)(reverse Coast Setting).By so doing, the dynamic advantages of coasting are more effectivelyimplemented within a reciprocating endodontic motor.

The program code embodied in any of the applications described herein iscapable of being distributed as a computer program product of variousdifferent forms. In particular, the program code may be distributedusing computer readable storage media. Computer readable storage mediaare inherently non-transitory, and may include volatile andnon-volatile, and removable and non-removable tangible media implementedin any manner. Computer readable storage media may further includerandom access memory, read-only memory, erasable programmable read-onlymemory, electrically erasable programmable read-only memory, flashmemory or other solid state memory technology, portable compact discread-only memory, or other optical storage, magnetic cassettes, magnetictape, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to store the desired information and thatcan be read by a computer. The program code may also be distributedusing communication media, which may embody computer readableinstructions, data structures, or other program modules. Communicationmedia may include wired and wireless media.

While the present invention has been illustrated by the description ofone or more embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus and methodand illustrative examples shown and described. Accordingly, departuresmay be made from such details without departing from the scope or spiritof the general inventive concept.

What is claimed is:
 1. An apparatus for controlling asymmetricalcoasting of an endodontic reciprocating motor, the apparatus comprising:an endodontic motor that is capable of rotating a tool in a clockwisedirection and in a counterclockwise direction, and a controller that isoperatively coupled to the endodontic motor and is capable of: (i)transmitting electronic signals to the endodontic motor to change thedirection of rotation of the tool from the clockwise direction to thecounterclockwise direction, (ii) controlling angular momentum of theendodontic motor in the clockwise direction to determine an amount ofdynamic angular rotation during a forward coast, and (iii) controllingangular momentum of the endodontic motor in the counterclockwisedirection to determine an amount of dynamic angular rotation during areverse coast, wherein the amount of dynamic angular rotation in theclockwise direction is different from the amount of dynamic angularrotation in the counterclockwise direction.
 2. The apparatus of claim 1wherein the controller is capable of directing the rotation of theendodontic motor in the clockwise direction independent of the rotationin the counterclockwise direction.
 3. The apparatus of claim 2 whereinthe controller includes a processing unit operatively coupled to theendodontic motor, the processing unit including a plurality of userselectable modes including a clockwise rotation mode, a counterclockwiserotation mode, and a reciprocating mode, and wherein the reciprocatingmode includes a user selectable forward endodontic motor speed and auser selectable reverse endodontic speed.
 4. The apparatus of claim 3wherein the processing unit is configured to calculate a forward coasttime based on the user selectable forward endodontic motor speed and tocalculate a reverse coast time based on the user selectable reverseendodontic motor speed, the forward coast time being different from thereverse coast time.
 5. A method for asymmetrically coasting areciprocating endodontic motor, comprising; rotating an endodontic motorin a forward direction; calculating an angular momentum for theendodontic motor in the forward direction; determining an amount ofdynamic angular rotation based on the angular momentum; coasting theendodontic motor in the forward direction according to the amount ofdynamic angular rotation; after coasting the endodontic motor in theforward direction, rotating the endodontic motor in a reverse direction;calculating an angular momentum for the endodontic motor in the reversedirection; determining an amount of dynamic angular rotation in thereverse direction based on the angular momentum in the reverse directionseparately from determining the amount of dynamic angular rotation inthe forward direction, the amount of dynamic angular rotation in thereverse direction being different than the amount of dynamic angularrotation in the forward direction; and coasting the endodontic motor inthe reverse direction for the amount of dynamic angular rotation in thereverse direction.
 6. The method of claim 5, further comprisingdetermining a forward coast time for the forward direction anddetermining a reverse coast time for the reverse direction.
 7. Themethod of claim 6 wherein prior to determining the amount of dynamicangular rotation in the forward direction, the method further comprises:selecting a forward coast setting and wherein determining the forwardcoast time includes calculating the forward coast time based on theforward coast setting.
 8. The method of claim 6 wherein prior todetermining the amount of dynamic angular rotation in the reversedirection, the method further comprises: selecting a reverse coastsetting and wherein determining the reverse coast time includescalculating the reverse coast time based on the reverse coast setting.9. The method of claim 6 wherein determining the forward coast timeincludes calculating the forward coast time based on a forward coastsetting and on a forward angular speed of the endodontic motor andwherein determining the reverse coast time includes calculating thereverse coast time based on a reverse coast setting and on a reverseangular speed of the endodontic motor.
 10. The method of claim 6 whereindetermining the forward coast time includes calculating the forwardcoast time by solving the equation:forward coast time =(−0.00005)(forward angularspeed)+(0.08)+(0.0044)(forward coast setting).
 11. The method of claim 6wherein determining the reverse coast time includes calculating thereverse coast time by solving the equation:reverse coast time =(−0.00005)(reverse angularspeed)+(0.08)+(0.0044)(reverse coast setting).
 12. The method of claim 5wherein after coasting the endodontic motor in the forward direction forthe amount of dynamic angular rotation and before rotating theendodontic motor in the reverse direction, the method further comprises:braking the endodontic motor to a stop.